JPH0366432A - Manufacture of hollow connecting rod and its device - Google Patents

Abstract

PURPOSE:To form a spherical surface excellent in working precision by expanding the diameters of both end parts of a prescribed metallic tube stock at a 1st stage and bending those end parts into a spherical shape at a 2nd stage. CONSTITUTION:The diameters of both ends of the tube stock 16 composed of carbon steel or other metallic materials cut to a prescribed length are expanded and formed by using a specific die assembly 30 to obtain an intermediate product 18. Then, both end parts of the intermediate product 18 are bent to form a spherical body 14 having spherical curved surfaces and to manufacture a hollow connected rod 10. In other words, the wall thickness of the expanded parts 20 at both end parts of the intermediate product 18 expanded in diameter and formed at the 1st stage are made thinner than that of the straight part 12. At the following 2nd stage, spherical bending is carried out by the full enclosed die forging using a similar die assembly 30 to the tube expanding part 20. Consequently, in the connecting rod 10, since the outer diameter of the spherical par 14 is larger than that of the straight part 12 and the thickness is not uniform, rigidity is improved and enough strength can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hollow connecting rod incorporated in a hydraulic continuously variable transmission, etc., and a method and apparatus for manufacturing the same.

[Prior Art] Conventionally, prior art related to the manufacturing method of this type of hollow connecting rod includes, for example, JP-A-59-185533, JP-A-59-185534, and JP-A-60-10.
The one disclosed in Japanese Patent No. 6635 is known.

These methods have in common that when forming a spherical part at the end of a tubular material by plastic working, the end is narrowly drawn and then compressed in the axial direction to form a curved surface.

In the hollow connecting rod obtained by applying such a method, the diameter of the spherical part is equal to or smaller than the diameter of the material. Further, the wall thickness of this spherical portion is approximately equal to the wall thickness of the material, and is also uniform.

[Problems to be Solved by the Invention] However, when the hollow connecting rod is in use, the force applied to the spherical part is concentrated on its end face, so forming the spherical part with an even thickness will cause the spherical part to There are limits to increasing the strength of

Further, it is desirable for the diameter of the spherical portion to be larger than the diameter of the rod portion from the viewpoint of strength.

The present invention has been made in view of this point, and the diameter of the spherical part at the end is larger than the diameter of the rod, and
It is an object of the present invention to provide a hollow connecting rod having a structure in which the wall thickness of a specific portion changes, and a method and apparatus for manufacturing the hollow connecting rod that enables the molding thereof.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a hollow connecting rod whose both ends are formed into spherical shapes by plastic working, including the following steps: The first step is to expand and form both ends of the tube, and the second step is to bend and form the expanded end into a spherical shape.
It is characterized by consisting of the following steps.

Further, the present invention provides a hollow connecting rod having a hollow rod portion and a spherical portion that bulges out in a spherical shape at both ends thereof, wherein the outer diameter of the spherical portion is larger than the outer diameter of the rod portion, and the spherical portion It is characterized in that a part of the wall is formed thinner than the wall of the neck.

Furthermore, the present invention provides a mold device that includes an upper mold that can be raised and lowered, a lower mold, and a split mold that moves in the horizontal direction. The present invention is characterized in that it includes a split mold that moves toward each other under the action of a cam as it descends, and that the cam has a multi-step cam surface.

[Function] In the manufacturing method of the present invention, when the tube is expanded in the first step, the end portion is formed into a thin wall, so in the second step, a spherical surface with good processing accuracy is formed, and the spherical portion is Since the outer diameter of the rod is larger than that of the rod and the wall thickness is not uniform, the rigidity is improved.

Further, in the manufacturing apparatus of the present invention, pressing force is applied from the vertical direction by a single drive source and from the horizontal direction by the split mold, and the impact at the time of mold clamping is alleviated by the multistage cam surface of the cam.

[Example] Next, a method and apparatus for manufacturing a hollow connecting rod according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a diagram showing a process of manufacturing a hollow connecting rod by plastic working, and FIG. 1C shows a hollow connecting rod 10 as a final product. This hollow connecting rod 10 consists of a pipe-shaped rod portion 12 that is hollow inside and spherical portions 14 at both ends thereof.

In this case, the spherical part 14 is formed in a bulging form so that the outer diameter of the spherical part 14 is larger than the outer diameter of the rod part 12.

Next, each process constituting the method for manufacturing such a hollow connecting rod 10 will be explained. That is, this manufacturing method is
A first step of forming an intermediate product 18 by performing tube expansion molding on both ends of a pipe-shaped material 16 made of carbon steel or other metal material cut to a predetermined length using a molding device to be described later; A second step includes bending both ends of the intermediate product 18 to form a spherical portion 14 having a spherical curved surface to obtain a hollow connecting rod 10.

First, in the first step, as shown in FIG. 2a,
The pipe-like material 16 is subjected to a tube-expansion forming process such that the wall thickness tl of the tube-expanded portions 20 formed at both ends of the intermediate product 180 becomes thinner than the wall thickness t of the rod portion 12.

The subsequent second step is also performed by closed forging using a similar mold device. Here, when performing spherical bending on the expanded tube part 20 of the intermediate product 18 to form the spherical part 14 of the hollow connecting rod 10, the wall thickness of each part of the spherical part 14 is set as follows.

That is, as shown in FIG. 2, this spherical portion 14
It is processed so that the wall thickness t2 near the top of is thicker than the wall thickness t3 near the center portion, and this wall thickness t3 is thinner than the wall thickness t of the neck portion 12.

Next, a mold apparatus used to perform the first step and second step as described above will be explained. In FIG. 3a, reference numeral 30 indicates the mold device, and this mold device 30 has an upper mold 36 attached to a ram-type piston 34 disposed on an elevating frame 32 of a press machine, and a bolster 38. It includes horizontally movable split molds 40a and 40b and a lower mold 42 fixed to a bolster 38.

The ram-shaped piston 34 is slidably fitted into a hydraulic cylinder chamber 44 for a cushion provided in the lifting frame 32, and an upper mold 36 fixed to the tip of the ram-shaped piston 34 is connected to a lower mold opposite thereto. 42 together with the collar 12 of the intermediate product 18
Apply preload to restrain.

In addition, in the lifting frame 32, the split molds 40a and 40b come into contact with the shoulders of the divided molds 40a and 40b, and as the lifting frame 32 descends, the divided molds 40a and 40b come into contact with each other.
cams 46a and 46 that displace b toward each other;
b is fixed. The cams 46a, 46b have at least two stages of cam surfaces 48, 50, as shown in FIG.
is formed. Regarding the angles θ0 and θ2 formed by the cam surface 48, 50 and the vertical plane, respectively, θ1 is determined to be a larger angle than 02, for example, θ is determined to be 30° and θ2 is determined to be 15°. The split mold 4 is arranged so that the inclined surfaces 52 and 54 corresponding to the cam surfaces 48 and 50 are continuous.
It is formed on the shoulders of 0a and 40b.

Here, an intermediate product 1
Insert mold 56 for molding the expanded tube portion 20 of No. 8
a and 56 b are installed, and this insert mold 56
a and 56b have a bulge n having a shape corresponding to the expanded tube portion 20.
57a and 57b are formed.

In this case, by exchanging the insert molds 56a, 56b with the insert molds 56c, 56d, etc., the first step and the second step can be performed in the mold apparatus 30. That is, as shown in FIG. 3, the insert mold 56c
, 56d are formed with recesses 58'a and 58b having a shape corresponding to the spherical part 14 of the hollow connecting rod 10, and the spherical recess 58a
, 58b has a protrusion 59a in the center to restrain the small hole.
59b is provided.

In addition, in such split molds 40 a and 4 (lb), return springs 62 a and 62 b that move the split molds 40 a and 40 b in the separating direction are housed in holes 60 a and 60 b defined below. In this case, the split molds 40a, 40b are configured to move along sliding guides 64a, 64b fixed on the bolster 38.

Regarding the operation of the mold device 30 configured as described above,
This will be explained below.

First, the pipe-shaped material 16 is positioned horizontally on the top of the lower mold 42 (see FIG. 3a). Thereafter, the elevating frame 32 is lowered, and the upper mold 36 at the tip of the ram-shaped piston 34 presses the rod portion 12 of the pipe-shaped material 16 in cooperation with the lower mold 42. Then, as this elevating frame 32 continues to descend, the upper die 36
The ram-type piston 34 to which is attached is located in the hydraulic cylinder chamber 44.
The pipe-shaped material 16 is displaced in the direction of the arrow to perform a cushioning action, and the pipe-shaped material 16 is placed under restraint by the cooperation of the upper mold 36 and the lower mold 42.

Next, when the elevator frame 32 further descends, this elevator frame 3
Since the cam surfaces 48 of the cams 46a and 46b provided in the split molds 40a and 40b slide along the corresponding inclined surfaces 52 formed on the shoulders of the split molds 40a and 40b, the split molds 4
0a and 40b are displaced in a direction toward each other against the elastic force of the return springs 62a and 62b, and machining of both ends of the pipe-shaped material 16 is simultaneously started by the respective insert molds 56a and 156b. In this manner, by the operation of the cams 46a146b, the elevating frame 32 can be pressed horizontally and vertically using only a single drive source that moves the elevating frame 32 up and down, and the structure is simplified.

After the tube expansion portions 20 are formed at both ends of the pipe-shaped material 16, when the elevating frame 32 rises, the split molds 40a140b are displaced in the mold opening direction by the elastic force of the return springs 62a and 62b, and the first step is completed. do.

Next, the insert molds 56a and 56b are replaced with insert molds 56c and 56d (see FIG. 3). Lower mold 4
The intermediate product 18 is placed on the hollow connecting rod I through the mold device 30 in the same procedure as the first step described above.
O is formed.

In the second step as described above, when the expanded tube portion 20 of the intermediate product 18 is processed into a spherical shape, since it has been thinly formed in the previous step, there is an advantage that the accuracy of the curved surface is improved. Also,
When the spherical part 14 is bent into a spherical shape, the thickness at the top of the spherical part 14 increases, which has the effect of increasing the rigidity compared to one with a uniform thickness.

In addition, in this case, the cams 46a and 46b have a two-stage cam surface, and at the final stage of machining,
The inclination angle θ of the cam surface 50 with respect to the vertical plane is the cam surface 48
Since the inclination angle θ1 is set small, it is possible to reduce the impact on the intermediate product 18 (and the pipe-shaped material 16) when it is finally held on the inner side surface of the cam 46a146b, and prevent galling. At the same time, the machining accuracy can be improved (see FIGS. 5 and 6).

Incidentally, such inclination angles θ1 and θ2 are determined by the split mold 40a,
It is set in consideration of the stroke of 40b, the mold clamping timing of upper mold 36, etc.

Next, another embodiment of the method for manufacturing the connecting rod will be described based on FIG. 7.

The manufacturing method according to the second embodiment involves performing tube expansion molding on both ends of a pipe-shaped material 16, and then forming a semi-closed secondary intermediate product 18a in which the expanded tube portion 20 of the intermediate product 18 is squeezed. After that, it is bent into a spherical shape in the same process as in the first embodiment.

When the outer diameter of the expanded tube part 20 is made particularly larger than the outer diameter of the rod part 12, the expanded tube part 20 is not immediately processed into a spherical shape as in the second embodiment, but is first squeezed and then processed. Spherical molding prevents problems such as buckling during spherical molding.

[Effects of the Invention] As described above, according to the present invention, the wall thickness at both ends is made thinner by performing expansion molding.
In addition to improving the accuracy of processing in the process, direct grinding reduces the number of processes and reduces production costs since thin-wall processing by other mechanical processes is not required. In addition, the outer diameter of the spherical part of the connecting rod manufactured in this way is larger than the outer diameter of the rod part, and the wall thickness is not uniform, so the rigidity is improved and sufficient strength can be obtained. This effect is achieved.

[Brief explanation of drawings]

FIG. 1 is a process diagram of the method for manufacturing a hollow connecting rod according to the present invention, 2nd TI! Ja is an enlarged sectional view of the main part of the intermediate product, Fig. 2 is an enlarged sectional view of the main part of the hollow connecting rod, Fig. 3a is a sectional view of the mold device used in the first process, and Fig. 3 is an enlarged sectional view of the main part of the intermediate product. FIG. 4 is a cross-sectional view of the mold device used in the second process. FIG. 4 is a diagram explaining the inclination angle of the cam surface of the cam provided in the mold device. FIGS. FIG. 7 is a cross-sectional view showing the state during processing in two steps. FIG. 7 is a process diagram of a method for manufacturing a hollow connecting rod according to another embodiment. 10... Hollow connecting rod 12... Rod part 14.
... Spherical part 16 ... Raw material 18 ... Intermediate product 18 ... Tube expansion part 30 ... Mold device 32 ... Lifting frame 34 ... Ram-shaped pistons 40a, 40b ... Split mold 46a , 46b...Cam 56a to 56d...Inser 36...Upper die 42...Lower die 48.50...Cam surface mold (Q) FIG, 1 (b) (C) FIG, 7 (C) (d)

Claims (5)

[Claims] (1) A method for manufacturing a hollow connecting rod with both ends formed into spherical shapes by plastic working, which includes: a first step of expanding both ends of a predetermined metal pipe-shaped material; and the expanded ends. The second step is to bend and form the material into a spherical shape.
A method for manufacturing a hollow connecting rod, comprising the steps of: (2) The method of manufacturing a hollow connecting rod according to claim 1, wherein a preliminary step of squeezing the expanded tube portion into a half-open shape is performed between the first step and the second step. (3) In a hollow connecting rod having a hollow rod portion and a spherical portion that bulges out into a spherical shape at both ends thereof, the outer diameter of the spherical portion is larger than the outer diameter of the rod portion, and a portion of the spherical portion A hollow connecting rod characterized in that the wall thickness of the rod is thinner than the wall thickness of the rod. (4) In a mold device equipped with an upper mold that can be raised and lowered, a lower mold, and a split mold that moves horizontally, a cam installed on the lifting frame to which the upper mold is attached and 1. A manufacturing apparatus comprising a split mold that moves toward each other under the action of a cam, the cam having a multi-step cam surface. (5) The manufacturing apparatus according to claim 4, characterized in that the intermediate product of the connecting rod is placed horizontally on the lower mold, and the split mold performs spherical bending on both ends of the intermediate product. Manufacturing equipment for